Pathways involved in pony body size development

Area of Science:

• Genetics and Molecular Biology
• Mammalian Physiology
• Endocrinology

Background:

• The mechanisms governing mammalian body growth remain largely unexplored.
• Investigating regulatory networks is crucial for understanding growth disparities.
• Transcriptomic analysis provides a powerful tool for dissecting complex biological processes.

Purpose of the Study:

• To elucidate the regulatory networks controlling body growth in mammals.
• To compare transcriptomic profiles of pituitary and epiphyseal tissues between smaller Debao ponies and larger Mongolian horses.
• To identify key genetic and hormonal factors contributing to variations in body size.

Main Methods:

• Transcriptomic analysis of pituitary and epiphyseal tissues.
• Quantitative PCR (q-PCR) and Western blot analyses.
• In vitro studies using WNT antagonists and GHR-RNAi lentiviral vectors.
• Hormone concentration measurements (IGF-1, GH).

Main Results:

• Low growth hormone receptor (GHR) expression in long bones of Debao ponies despite high growth hormone (GH) levels.
• Downregulation of GHR pathway components (m-RAS, ATF3) and upregulation of WNT2 and PLCβ2 in juvenile ponies, impacting bone cell proliferation and mineralization.
• Evidence suggesting the WNT/Ca2+ pathway regulates body growth.
• Lower IGF-1 gene expression in Debao ponies' livers compared to Mongolian horses.
• Distinct hormonal profiles: higher IGF-1 in juvenile Debao ponies and higher GH in adult Debao ponies.

Conclusions:

• The study provides novel insights into the genetic regulation of short stature in mammals.
• Identified key molecular players, including GHR and the WNT/Ca2+ pathway, in controlling body size.
• Findings can inform the development of therapeutic strategies for growth-related conditions.